Conventionally, the majority of the heating and cooling or air conditioning devices operating in room temperature range such as refrigerators, freezers, and air conditioners take advantage of the thermal conductivity of a gas refrigerant like chlorofluorocarbon (CFC) and alternative chlorofluorocarbon gas. More recently, the problem of ozone depletion caused by the discharge of Freon gas is known, and further, the effects of global warming due to discharge of alternative Freon is also a concern. Therefore, the development of an air conditioning device which is clean and innovative with high heat transfer capacity is strongly desired as an alternative to the refrigerator using the gaseous refrigerant and causing the high environmental loads due to use of CFC or alternative for CFC.
Against this background, air conditioning technology that is now attracting attention recently is a magnetic heating and cooling technology. Some of the magnetic material exhibits, when the magnitude of the magnetic field applied to the magnetic body is changed, vary temperature of itself in response to that change, through so-called magneto-caloric effect. The magnetic conditioning device technology is directed to such technology for transporting heat by using a magnetic material expressing the magneto-caloric effect.
For refrigerator utilizing gaseous refrigerant, it is necessary to use a gas refrigerant of large environmental load in order to establish a refrigeration cycle. Moreover, a step of compressing the gaseous refrigerant is required. However, in the case of a magnetic refrigerator utilizing a magnetocaloric effect, it is sufficient to use a liquid refrigerant (usually water or water plus alcohol) with low environmental hazard in order to establish a magnetic refrigeration cycle and to move the liquid refrigerant two-way, i.e. between a high and low temperature sides.
In this way, the magnetic refrigerator is attracting attention as a refrigerator for the next generation because it does not only cause problems of ozone layer depletion and global warming but also has high energy efficiency.
In the magnetic refrigeration technology that targets the room temperature region, for example, an AMR (Active-Magnetic Regenerative Refrigeration) method as described in International Publication No. WO2010/034 907 is known. The AMR method is a magnetic refrigeration technology that not only uses a magnetic material as the magnetic refrigeration material to exhibit the magnetocaloric effect in the magnetic material but also exhibits a regenerative effect of storing heat generated by the magnetic material.
In order to combine the magnetocaloric effect and regenerative effect to thereby produce a favorable temperature gradient for the heat transport throughout a magnetic refrigeration material in the AMR method, the thermal conductivity of the magnetic refrigeration material is controlled.
However, there is room for improvement in enhancement of heat exchange efficiency in the magnetic refrigerator having high energy efficiency.
In the case of the conventional magnetic refrigerator, a plurality of magnetic bodies of the flat plate are laminated on one another with a gap interposed there between and a liquid refrigerant is passed through in the gap to be subjected to heat exchange between the magnetic body and the liquid refrigerant. Heat exchange efficiency between the magnetic material and liquid refrigerant can be improved by exploring for a high frequency of the reciprocating movement of the liquid refrigerant, specifically through the optimization of its reciprocating distance and period. However, there is a limit on the improvement in the heat exchange efficiency only through high frequency by optimizing the distance or period.